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1'32                         METALLURGY OIMROF AND STEEL.
into two compartments by a vertical wall, and separate flues run from the valve to each. The results indicate that a saving of fuel follows this construction. It often happens that it is impossible to build a furnace exactly as desired. This was the case in Pigs. VIII-B and VIII-C, for permanent water existed only fifteen feet below the general level, and it was difficult to get sufficient room for checkers. In this case the air is blown by a centrifugal fan, the pressure being very low.
Fig. VIII-D shows the method of construction for basic furnaces at Donawitz, Austria, where the practice is excellent both in life of furnace and amount of product. Fig. VIII-E shows the 50-ton basic furnaces at Duquesne, Pa., and Fig. VIII-F those at Sharon, Pa. The drawing of the Duquesne furnace shows how the capacity of the chambers may be decreased when natural gas is used, as both regenerators are available for heating the air.
SEC. Vllld.—Tilting open-hearth furnace.—Many years ago I put in operation the first tilting open-hearth furnace, while a, few years afterwards Mr. Wellman built a similar furnace, but used a different system of tilting. In the original type the furnace sits on live rollers running on circular paths; the center of these circular arcs is coincident with the center of the port through which the gas and air enter the furnace, so that the opening in the end of the furnace coincides with the port opening, no matter what position the furnace may occupy, and for this reason there is no occasion to cut off the gas and air when the furnace is rotated. In the Wellman type the furnace rolls forward upon a horizontal track and it is necessary to shut off the gas and air as soon as the furnace is tipped from its normal position.
I have often been asked to compare the relative advantages of these two types, and although evidently I cannot render a judicial and unbiased judgment, it may be proper to express my opinions, whether they be judicial or not.
(1)   Both types of tilting furnaces do away with most of the work and delay connected with the tap-hole, and when the bottom is good the next charge can be put in as soon as the metal is tapped.
(2)   If the bottom is bad, especially when there is a hole in the flat, a stationary furnace is often delayed by the tap-hole.    In a tilting furnace of either-type a hole can be drained dry by tilting the furnace and repaired in that position,